Re: enq: tx - contention on selects

From: <srivenu_at_hotmail.com>
Date: Tue, 16 Sep 2008 11:59:49 -0700 (PDT)
Message-ID: <fae01a0b-1608-4a93-96b2-c3a5ef7a1425@w24g2000prd.googlegroups.com>

selects across db links can wait for TX locks (mode 4). This is the only instance in oracle where a select can be locked.

Since your problem is frequent, this could be a flaky network causing a lot of distributed transactions to go into a pending state. Once a transaction goes into a pending state, other sessions trying to access that data may wait with TX mode 4. You can monitor DBA_2PC_PENDING & DBA_2PC_NEIGHBORS. regards
srivenu Received on Tue Sep 16 2008 - 13:59:49 CDT

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